Manufacturing specifications for enclosed volumes often require that the enclosed volumes be essentially leak-free, with little or no tolerance for escaping gases of any kind or amount. As used herein, the term “enclosed volume” may refer to any volume defined within an enclosure made up of one or more walls that surround or otherwise substantially isolate the enclosed volume. Common types of enclosed volumes include, but are not limited to, gas storage vessels, fuel cell compartments, vehicle engine components, battery enclosures, and vacuum reactors. It is well known that covers enclosing electric-vehicle batteries (for example batteries falling into a class of rechargeable energy storage systems (RESS)) must be completely impervious to leaks to ensure proper operation of the batteries. To determine whether these or any other type of enclosed volume contains leaks, the manufacturer often requires as a quality control validation that one or more leak-testing methods be employed.
One type of leak-testing method may involve first isolating the enclosure, with the enclosed volume therein, within a secondary enclosure that itself is isolated from the external environment. A suitable tracer gas may be added by any means into the enclosed volume, so as to pressurize the enclosed volume slightly with due care not to exceed a pressure that may compromise the walls of the enclosure in any way. The tracer gas typically is a low molecular-weight, inert gas such as helium, which diffuses readily through any pinpoint leaks present in the outer wall around the enclosed volume. If tracer gas escapes through a leak in the outer wall, its presence can be detected within the secondary enclosure by sensitive instruments such as a mass spectrometer. If no leak is detected, the tracer gas can be removed from the enclosed volume and the outer wall can be said to have passed quality control. However, in such a test configuration, a false-positive determination of a defective outer wall can result if the means for adding the tracer gas into the enclosed volume itself has a leak that allows tracer gas to enter the secondary enclosure. If the leak is severe, the tracer gas can contaminate the secondary enclosure and require time-consuming purge cycles before further testing can resume. Even so, tools or process steps necessary to ensure leak-free input of the tracer gas into the enclosed volume also can add time and expense to the leak-testing process.
Therefore, there is an ongoing need for tools that facilitate during leak-testing operations the introduction of tracer gases into enclosed volumes and the removal of the tracer gases from the enclosed volumes without leakage around the tool. Furthermore, there remains an ongoing need for systems incorporating such tools and methods for leak testing that employ the tools in a low-cost, simplified manner.